He was asked why house to house inquiries and vehicle checkpoints in the area stopped so quickly after the attack.

Other leads not followed up, he confirmed, were a large gathering of men with a suspect van in a Silverbridge yard shortly before the attack; the getaway minibus seen at the home of suspect S89; a driver stopped by the gunmen; suspect S104 – who was unknown to him, and a report the gang fled over fields via Carricknanny Chapel.

But Mr Mitchell said he had only 12 detectives to deal with regular crime as well as a further 29 murders and Kingsmills; in modern terms this would require 50 detectives. Requests for more staff were refused.

Looking back now he feels “regret” that there was “no justice” for the families.

He did not accept that the atrocity had been in retaliation to the murders of the Reavey brothers at Whitecross and O’Dowds in Lurgan by loyalists the day before; Kingsmills would have required much more than 24 hours planning, he said.